Organic molecules can be designed to alter reversibly their ability to absorb electromagnetic radiation in response to electricity (electrochromism), heat (thermochromism), light (photochromism), and pH (halochromism). Such energy-induced transformations can be used to switch the color of liquid, gel-sol, or solid samples under the influence of external stimulation. As a result, electrochromic, thermochromic, photochromic, and halochromic molecules can be exploited to design stimuli responsive materials for a diversity of applications. For example, displays, filters, indicators, lenses, sensors, switches, and windows may be developed relying on these functional compounds. In addition to such chromogenic materials, post-application color-changing films (e.g., solid) or coatings (e.g., liquid or gel-sol) can be designed around the functional molecules. For example, appropriate formulations of these functional molecules may be applied on the surface of a solid substrate as a film, gel-sol, or coating, and then the color of the chromogenic material may be controlled reversibly with electricity, heat, light, or pH. On the basis of these considerations, our heterocyclic compounds with halochromic response may be used to make chromogenic materials. In principle, these molecules can be the basic building blocks for the development of pH-sensitive and chromogenic coatings.